Why Are Kenyan Coffee Beans Acidic? The Impact of Water Quality, Roast Level, and Pouring Technique on Brewed Coffee Flavor

After introducing so many coffee beans to everyone, FrontStreet Coffee would like to test your knowledge: Which coffee-growing region in the world produces coffee with the highest acidity? Many customers have provided feedback to FrontStreet Coffee that the acidity of Kenyan coffee they've purchased is more pronounced than other coffee beans. Indeed, during cupping sessions at FrontStreet Coffee, we can distinctly perceive the tomato, citrus, and lemon notes in Kenyan coffee—truly a blessing for acidity enthusiasts. So why is Kenyan coffee so acidic? And what other coffees have similar acidity? Today, FrontStreet Coffee will answer these questions for you.

The Remarkable Origins of Kenyan Coffee

Without a doubt: Kenya is an amazing coffee-producing region. Coffee from this origin is renowned for its rich aroma, refreshing acidity, sweet berry flavors, full body, and clean, lingering aftertaste. Therefore, let's first start with the origin itself. Kenyan Arabica coffee grows in the fertile volcanic soil of highlands at elevations between 1,400 and 2,000 meters. Both altitude and volcanic soil affect the flavor profile.

FrontStreet Coffee believes that high altitude is one of the important factors contributing to the quality of Kenya AA coffee. The higher the altitude, the lower the temperature and the less oxygen. Coffee trees growing in such conditions develop more slowly, meaning the coffee has more time to absorb nutrients. Furthermore, the high phosphate content in the soil is one of the main sources of acidity in Kenyan coffee.

Phosphoric acid is less stimulating than citric and acetic acids, making the acidity characteristics of Kenya AA coffee bright but not overpowering. Mount Kenya is an inactive volcano rich in minerals. The highland air is often cloudy, and sunlight diffuses through the thin atmosphere, creating cool temperatures, especially at night. Similar to how fruits in Xinjiang are exceptionally sweet due to large temperature differences between day and night, Kenyan coffee cherries develop more sugars during the night. The beans develop intense fruity acidity, combined with a full body and rich aroma.

According to FrontStreet Coffee's understanding, Kenyan coffee is typically grown by smallholder farmers. Kenyan producers value quality, therefore, processing and drying procedures are carefully controlled and monitored. In Kenya, a "coffee batch" is made from larger quantities of coffee delivered from cooperatives to the dry mill on a given day. When a batch arrives at the mill, it is processed (hulled), analyzed (technically and sensorially), screened (separated by bean size), and given a final count. When parchment is removed from the beans during hulling, the beans are screened and separated by shape and size. This maximizes the preservation of coffee quality. Good management at quality factories doesn't allow unripe or unevenly ripe cherries. This is because accepting such cherries would compromise the potential for everyone involved to get the best price.

Kenyan Coffee Processing and Grading

In the Kenyan coffee market, the price of coffee cherries is directly related to cup quality. Most Kenyan coffee beans are washed processed. Taking FrontStreet Coffee's Asalia as an example, it uses the K72 processing method. This is a special coffee processing method. Unlike traditional washed processing, the cleaned coffee beans need to be soaked in clean water tanks for 24 hours, then cleaned and repeat this step more than three times, totaling 72 hours, thus it's also known as the "K72" processing method. It's time-consuming and labor-intensive, which is why Kenyan coffee beans are relatively more expensive. FrontStreet Coffee believes this also contributes to the superior acidity of Kenyan coffee.

The Impact of Roasting on Acidity

Roasting is also a factor that contributes to the acidity of Kenyan coffee. Some believe that acidity gives coffee its vitality. So why do most coffee roasters use light roasts for beans with floral and fruity flavor profiles?

FrontStreet Coffee believes we should look at the chemical reactions during the coffee bean roasting process. Chlorogenic acid is currently the most common acid found in green beans. Coffee gradually breaks down chlorogenic acid during the roasting process. The concentration of acidity typically peaks at very light roast levels and then gradually decreases as roasting time increases. The roasting profile designed by FrontStreet Coffee for Asalia significantly amplifies the acidic characteristics of Kenyan coffee. The coffee roasting process begins with green coffee beans. Through the perfect balance of heat, air, rotation, and other factors, the roaster transforms these green beans into the coffee we know and love. In coffee, the Maillard reaction converts the original organic compounds in green coffee into delicious flavors and caramelizes sugars. Without the Maillard reaction, coffee would taste distinctly acidic and perhaps somewhat raw.

Home Brewing Factors That Affect Acidity

For those who make coffee at home, FrontStreet Coffee believes there are other factors that affect coffee flavor that are often overlooked by beginners: brewing water and extraction methods. Let's first talk about brewing water. In recent years, in various coffee brewing competitions, brewing water has become an area of focus for many baristas, who customize their own coffee brewing water.

As we all know, a cup of coffee is 98% water, and water plays an important role in the coffee brewing process. Home brewing water must ensure quality and stability. So what's the best water to use when brewing coffee? Typically, we have three choices: filtered water, distilled water, and purified water. FrontStreet Coffee believes we need to look at the TDS value (Total Dissolved Solids) in the water, which are usually composed of magnesium, calcium, and bicarbonates. pH value is also something we need to pay attention to. FrontStreet Coffee believes that a pH value between 6.5-7.5 is acceptable. At a neutral pH, the ideal water for making coffee should have a Total Dissolved Solids (TDS) of about 150 mg/L. You also need approximately 10 mg/L of sodium, 40 mg/L of total alkalinity, and 0 mg/L of chlorine. FrontStreet Coffee gives everyone a direct recommendation: Nongfu Spring Water. For home or commercial coffee brewing, Nongfu Spring's TDS value is closest to the standard brewing water and can bring out the aromatic soluble compounds in coffee.

Now let's talk about the issue of extraction. A common cause of acidic coffee is under-extraction during the brewing process. This happens when enough flavor isn't extracted from the coffee grounds during brewing. The longer the coffee brews, the more sugars are extracted from the grounds, making the coffee taste sweeter. However, if the time is too long, bitterness will eventually appear (over-extraction). In this situation, adjusting the grind size or water temperature is recommended.

When purchasing coffee at FrontStreet Coffee stores, you can ask for the coffee to be ground. Of course, if you have specific requirements for coffee taste and hope to grind your own coffee, FrontStreet Coffee suggests buying a standard #20 sieve to screen the grounds. Taking FrontStreet Coffee's Asalia as an example, a screening rate of 75%-80% would be reasonable. The finer the grind, the larger the surface area of the coffee beans, increasing the extraction rate. Therefore, with all other conditions being equal, changing the grind size will also change the flavor of the brewed coffee. If the coffee flavor is too acidic, grinding it coarser will help. FrontStreet Coffee has provided detailed explanations of factors affecting coffee flavor during brewing in previous articles. If interested, you can look them up.

If we don't have such equipment at home but want to quickly verify whether the grind size is correct, we can judge whether the grind is too coarse, too fine, or just right by combining the particle morphology and duration during the extraction phase. Because regardless of the particle size distribution, we still need to test based on the formal brewing stages and final flavor performance. At this point, we can use the morphology of suspended particles during blooming, total drip time, and the size of coffee ground particles to find the answer.

Here, FrontStreet Coffee uses Kenya Asalia as the brewing protagonist to demonstrate how to test for the ideal grind setting when faced with an unfamiliar hand grinder.

First, the particles ground at the first setting were mostly chunky, clearly approaching sea salt texture, so a significant adjustment to finer was needed. Here, FrontStreet Coffee adjusted 10 clicks toward the finer direction, and the resulting powder was close to fine sugar size, which meets the requirements for pour-over grinding. At this point, we can proceed to the extraction phase to verify it.

Coffee beans: 15 grams
Total water: 225 grams
Water temperature: 91°C
Three-stage pour: 30 grams, 95 grams, 100 grams

During the blooming phase, the particles were tightly connected with high water retention. As the pour approached the end, the flow rate significantly slowed, and the filter paper was likely clogged by a large amount of very fine particles, with extraction time exceeding 2.5 minutes. From the spent coffee grounds, we could see mud powder floating on the surface, and the coffee had a heavy berry flavor with a slightly astringent aftertaste. This indicated that the grind was too fine, causing over-extraction, so it needed to be adjusted slightly coarser. Here, FrontStreet Coffee adjusted 3 clicks coarser to continue testing.

With the same brewing parameters, the coffee grounds at the new setting had looser gaps between suspended particles during blooming, with high water permeability. The flow rate was uniform throughout the pouring process, with a total extraction time of 2 minutes and 8 seconds. The spent coffee grounds were fluffy and evenly distributed on the dripper wall. The coffee had moderate concentration, with citrus fruit sweetness and sourness and a caramel aftertaste. This indicated that we had found the ideal grind size.

Conclusion

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat official account: cafe_style). For more specialty coffee beans, please add FrontStreet Coffee's private WeChat account: kaixinguoguo0925

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